Production of jet fuel



1963 F. G. CIAPETTA ETAL 3,111,482

PRODUCTION OF JET FUEL Filed July 12, 1960 H RECYCLE RECYGLE lnven/ors Fran/r 6. C/apel/a Harry L. Coonrad/ M/l/amE Garwood Al/omey flit rates This application is a continuation-in-part of application Serial Number 582,732, filed May 4, 1956, now abandoned.

This invention is directed to fuels utilizable in jet com bustion devices. it is more particularly concerned with novel jet fuels and a method of producing them that have a combination of improved characteristics.

As is well known to those familiar with the art, the term jet combustion refers to a method of combustion wherein fuel is continuously introduced into and continuously burned in a confined space, for the purpose of deriving power directly from the hot products of combustion. The most complicated forms of jet engines pre ently proposed consist of a propulsion or jet tube, closed at one end, plus a gas turbine which extracts sufficient energy from the departing gases to drive the compressor. In present commercial forms, the compressor and turbine are assembled axially upon a common shaft, spaced far enough apart to permit a number of combustion chambers to be arranged about the shaft between the compressor and turbine, with an exhaust tube extending rearwardly from the turbine. The principal application of such engines is in powering aircraft, panticularly for high altitude operations. Therefore, the desiderata of fuels utilizable in jet combustion devices are many and varied.

In copending application Serial Number 541,734, filed October 20, 1955, there were disclosed novel jet fuels having a variety of improved properties. These fuels were produced by cracking certain petroleum fractions in the presence of hydrogen and of catalysts comprising metals of the platinum or palladium series deposited upon a refractory acidic oxide carrier. It was disclosed, however, that gas oils having an end point greater than about 760 F generally could not be cracked in a once-through operation to produce the jet fuels having all the improved characteristics.

It has now been found that the propenties of jet fuels that are produced by cracking a high boiling charge stock in a once through operation in the presence of hydrogen and a cracking catalyst, preferably a platinum or palladium series metal catalyst, can be markedly improved by a method that is simple and economical. It has been discovered that when at least a substantial part of the portion of a lower boiling range jet fuel, so obtained, that boils in the naphtha boiling range is replaced by straight run naphtha, the properties of the jet fuel are greatly improved. It is also a feature of this invention that the cracked naptha, thus obtained, can be reformed to produce large yields of high octane gasoline and of hydrogen than can be used to supply all or a part of the hydrogen consumed in the cracking operation.

Accordingly, it is an object of this invention to provide an improved jet combustion fuel. Another object is to provide a simple process for producing an improved lower boiling range jet fuel. A further object is to provide a jet fuel of improved properties that is obtained by cracking in the presence of hydrogen and of a suitable cracking catalyst. A specific object is to provide a jet fuel having improved properties that is obtained by cracking in the presence of a catalyst that contains a platinum or palladium series metal. Another specific object is to provide a. method for producing improved jet combustion fuels and high octane gasoline that involves cracking higher boiling arena charge stocks in the presence of hydrogen and of cracking catalysts, preferably the platinum and palladium series metal catalysts, replacing the portion of the jet fuel boiling in the naphtha boiling range with straight run naphtha, and reforming the cracked naphtha to produce high octane gasoline and hydrogen for use in the cracking step. A further specific object is to provide improved jet combustion fuels that are produced by such process.

Other objects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description considered in conjunction with the drawing which ShOWs a schematic arrangement of a typical embodiment for carrying out the process of this invention.

In general, the present invention provides a novel jet fuel and a method for producing it that comprises con tacting a hydrocarbon charge stock with a cracking catalyst, preferably one that comprises between about 0.05 percent and about 20 percent, by weight of the catalyst, of at least one metal of the platinum and palladium series deposited upon a synthetic composite of the solid oxides of at least two elements of groups *IIA, :lIIB and IV of the periodic arrangement of the elements, said composite having an activity index of at least 25, in the presence of hydrogen in amounts, expressed in molar ratio of hydrogen to hydrocarbon charge, within the range about 2 to about 80, at pressures within the range about p.s.i.g. to about 2500 p.s.i.g. and higher, at a liquid hourly space velocity within the mange about 0.1 to about 10, and at a temperature within the range about 500 'F. to about 1200 F; and correlating said temperature with said liquid hourly space velocity to convert at least a portion of the hydrocarbon charge into a jet fuel having an initial boiling point falling within the range about F. to about 225 F. and an end boiling point falling within the range about 450 F. to about 550 F., separating from the fuel a naphtha fraction that has an initial boiling point falling within the range about 160 F. to about 225 F. and an end boiling point falling Within the range about 350 F. to about 425 F, and replacing said fraction in the fuel with a straight run distillate naphtha that has an initial boiling point falling within the range about 160 F. to about 225 F. and an end boiling point falling within the range about 350 F. to about 425 F.

Throughout the specification and the claims, dry gas refers to the methane, ethane, propane and ethylene and propylene produced in a cracking process, expressed in terms of weight percent of the initial charge. Light naphtha boils in the range about 80 F. to about 160- 225 F. The heavy naphtha fraction boils in the range about 160-225 F. to about 350425 F. The anilinegravity product is expressed as the product of the A.P.I. gravity and the aniline number, as described in ASTM test methods D611 and D287. The smoke volatility index is obtained by adding to the smoke point (method 2107 of Federal Specification VV-L-79l) 0.42 times the volume percent of the fuel boiling under 400 F. The cracking activity of a carrier for the preferred cracking catalyst used herein is expressed in terms of the percent, by volume, of a standard hydrocarbon charge which is cracked, under specific conditions, in the Cat A test. This test is described by Alexander and Shimp in National Petroleum News, 36, page R537 (August 2, 1944). The unit for rating the cracking activity of such a carrier is called the activity index (A.I.).

The jet fuel that are contemplated herein are the lower boiling range fuels. They have an initial boiling point falling within the range about 160 F. to about 225 F. The end boiling point falls within the range about 45 0 F. to about 550 F. These fuels boil substantially continuously between the initial boiling point and the end boiling point. A typical jet fuel of this type is the IP4 fuel as defined in Military Specification MIL-F-S 624B. The jets fuels of this invention are not restricted to these military specifications, however, as the specifications are tentative. The present invention provides superior jet fuels that can boil at temperatures differing from the tentative specifications.

The jet fuels that are improved by the process of this invention are produced by cracking a gas oil in the presence of hydrogen and of suitable cracking catalysts. As is well known to those familiar with the art, the jet fuels that are produced in the presence of various catalysts are not necessarily equivalent in their properties, i.e., some catalysts effect the production of jet fuels having better qualities and properties than those produced in the presence of certain other catalysts. In any event, however, any jet fuel that has been produced by cracking in the presence of hydrogen can be improved by means of the process of this invention.

A number of catalysts that are effective for cracking in the presence of hydrogen are known to the art. Suitable catalysts comprise a mixture of one or more compounds, preferably the oxides or sulfides, of molybdenum, chromium, tungsten, vanadium, iron, nickel and cobalt; and metallic nickel, iron and cobalt. Very often these materials are used on supports or carriers, such as silica, alumina, pumice, charcoal, clays and the like.

As was disclosed in copending application Serial Number 541,734, filed October 20, 1955, superior jet fuels are produced by cracking in the presence of certain platinum and palladium series metal-containing catalysts.

The catalysts utilizable are those described in copending application Serial Number 825,016, filed July 6, 1959, now Patent No. 2,945,806. Briefly, these catalysts comprise between about 0.05 percent, by weight, and about 20 percent, by weight of the final catalyst, preferably between about 0.1 percent and about 5 percent, by weight, of the metals of the platinum and palladium series, i.e., those having atomic numbers of 44-46, inclusive, 7 678, inclusive, supported upon synthetic composites of two or more refractory oxides. The carrier is a synthetic composite of two or more oxides of the metals of groups IIA, IHB and IVA and B of the periodic arrangement of elements [1. Chem. Ed., 16, 409 (1939)]. These synthetic composites of refractory oxides must have an activity index greater than about 25. They can also contain halogens and other materials which are known in the art as promoters for cracking catalysts, or small amounts of alkali metals that are added for the purpose of controlling the activity index of the carrier. Non-limiting examples of the composites contemplated herein include silicaalumina, silica-Zirconia, silica-alumina-zirconia, alumina boria, silica-alumina-fiuorine, and the like. The preferred support is a synthetic composite of silica and alumina containing between about 1 percent, by weight, and about 90 percent, by weight, of alumina. 'Ihese synthetic composites of two or more refractory oxides can be made by any of the usual methods known to those skilled in the art of catalyst manufacture. Examples of methods of preparing them are set forth in copending application Serial Number 825,016.

The following example illustrates a method of preparing a platinum-containing catalyst utilizable in the process of this invention:

EXAMPLE 1 A synthetic silica-alumina carrier or support containing percent, by weight, alumina was prepared by mixing an aqueous solution of sodium silicate (containing 158 g. per liter of silica) with an equal amount of an aqueous acid solution of aluminum sulfate containing 39.4 g. Al (SO and 28.6. g. concentrated H 30 per liter. The mixture was dropped through a column of oil wherein gelation of the hydrogel was effected in head form. The head hydrogel was soaked in hot water (about 120 F.) for about 3 hours. The sodium in the hydrogel was then removed by exchanging the gel with an aqueous solution of aluminum sulfate [1.5 percent Al (SO by weight] containing a small amount (0.2 percent by weight) of ammonium sulfate. The thus-exchanged hydrogel head was waterwashed. Then, it was dried in superheated steam (about 280-340" F.) for about 3 hours and, finally, calcined at 1300 F. under a low partial pressure of steam for about 10 hours. The silica-alumina beads were then crushed to pass through a 14-mesh screen and the material retained on a ZS-mesh screen (U.S. standard screen series) was used for catalyst preparation.

Portions of the crushed, calcined carrier were then barely covered with aqueous solutions of chloroplatinic acid, of concentrations sufficient to produce the desired amount of metal in the finished catalyst. The excess solution was removed by centrifuging. The thus impregnated carrier was then dried at 230 F. for 24 hours. The catalyst was treated with hydrogen for 4 hours at 400 P. Then it was activated in hydrogen for 16 hours before it was used. The catalyst thus prepared contained 0.47 percent platinum, by weight, of the catalyst, and the silicaalumina carrier had an activity index of 46.

The cracking operation used in the process of this invention is carried out in the presence of hydrogen in amounts, expressed as the molar ratio of hydrogen to hydrocarbon charge, within the range about 2 to about 80, preferably between about 5 and about 50. The liquid hourly space velocity will be within the range about 0.1 about 10, preferably between 0.1 and about 5. When the aforedescribed platinum or palladium series metal catalysts are used, the cracking temperature may be any of the temperatures known in the art for hydrocracking but will preferably be within the range about 500 F. to about 825 F., still more preferably between about 600 F. and about 775 F. The hydrogen pressure can be within the range about p.s.i.g. to about 2500 p.s.i.g. or higher, preferably within the range about 350 to 2000 p.s.i.g. When the cracking operation, however, is carried out in the presence of other type catalysts, such as the oxides and sulfides of the various metals listed hereinbefore, the temperatures for cracking are usually much higher. Thus, in cracking in the presence of hydrogen with such catalysts, temperatures from about 600 F. to 900 F. are preferred but temperatures up to 1200 F. may be required and, generally, pressures in the order of 50010,000 p.s.i.g. will be used.

The charge stocks contemplated for use in the process of this invention are hydrocarbon fractions that have an end boiling point greater than about 760 F. These materials can have initial boiling points of 400 F. or higher. Accordingly, the stocks contemplated include a heavy gas oil which boils between about 600650 F. and about 800900 F., and a vacuum gas oil boiling between about 800-850 F. and about 11001200 F. It must be understood, however, that the charge can overlap the foregoing boiling ranges. It can even span other ranges that include, for example, medium and heavy gas oils. Another material that is utilizable herein is a whole topped crude that has been deasphalted. This material is the entire portion of the crude remaining after the light ends have been removed by distillation. Such a fraction, therefore, will boil between about 400 F. up to 1l001200 F. and higher. Refractory cycle stocks obtained from conventionally cracked stocks are also contemplated. These materials usually boil between about 400 F. and about 850 F.

The process of this invention will be understood from FIGURE 1. in FIGURE 1 there is presented a schematic arrangement of a method for carrying out the process of the present invention. The hydrocarbon charge is introduced through a pipe 10 and pumped by means of a suitable pumping device 11 through a pipe 12 into a heater 13. In the heater 13 the charge stock is heated to reaction temperature. The thus heated charge stock then is passed through pipes 14 and 15 into a reactor 16.

Hydrogen gas, or a gas rich in hydrogen, is introduced through a pipe 17 and pumped and compressed by means of a compressor 18. The compressed hydrogen then passes through a pipe 19 into a heat exchanger or heating device 20 wherein it is heated to reaction temperature. The thus heated hydrogen is then commingled with the hydrocarbon charge in pipe 15 and the mixture passes into the reactor 16.

In the reactor 16 there is a bed of suitable cracking catalyst, preferably a platinum or palladium series metal catalyst, as described hereinbefore. The mixture of hydrogen and hydrocarbon charge is contacted with the catalyst in the reactor 16 under conditions, falling Within the ranges set forth hereinbefore, to effect at least partial conversion of the hydrocarbon charge into a lower boiling range jet fuel. It will be understood, of course, that the degree of conversion used would depend upon the amount of jet fuel desired. In an extreme case, the entire charge material can be converted into products boiling in the jet fuel range, i.e., at temperatures below about 550 F. The total effluent from the reactor 16 is removed through a pipe 21 and passed into a heat exchanger or suitable cooling device 22. In the heat exchanger 22, the efiluent is cooled to temperatures at which gaseous hydrogen can be separated from the liquid phase. The thus cooled effluent is passed through a pipe 23 into a high pressure separator 24.

In the high pressure separator 24 there are a liquid phase and a gaseous phase. The gaseous phase containing substantial amounts of hydrogen is removed through a pipe 25 and can be recycled to the process through pipe 19.

The liquid product from the high pressure separator 24 is removed through pipe 26, passed through a depressuring zone 27 and thence to a pipe 28 into a suitable fractionating device 29. In the fractionator 29, the liquid products are separated into suitable fractions. Dry gas is removed through a pipe 30 and can be sent to the gas processing plant. The butanes are removed through a pipe 31 and light naphtha is removed through a pipe 32. A heavy naphtha is removed through a pipe 33. A fraction boiling at temperatures Within the range about 350425 F. to about 450550 F. is removed through a pipe 34. The material boiling at temperatures higher than about 550 F. can be removed through a pipe 35. If desired, this material can be recycled to the process through a pipe 36.

The naphtha, boiling at temperatures within the range about 125225 F. to about 350-425 F., that is removed through pipe 33 and the fraction removed through pipe 34, together constitute a lower boiling range jet fuel. The jet fuel of this invention, however, is not obtained entirely from the process. The fraction boiling at temperatures within the range about 350-425 F. to about 450550 F. is passed through the pipe 34 into a jet fuel blending operation 37.

In this operation a straight run naphtha is introduced through a pipe 38 and blended with the fraction introduced through pipe 34 to produce the jet fuel of this invention. This fuel is removed through a pipe 39. The straight run naphtha that is introduced through pipe 38 is a material that boils within the range about 160- 225 F. to about 350425 F. that is obtained by distillation of a virgin crude. Usually this naphtha has sub-- stanitally the same boiling range as the cracked naphtha that is removed through pipe 33. This naphtha can be obtained from the same crude source as the hydrocarbon chmge stock introduced through pipe 10 or it can be of a different source.

It will generally be desirable and preferred to replace all of the hydrocracked naphtha with straight run naphtha; however, within the broad scope of this invention only a part of the hydrocracked naphtha need be replaced. Some of the hydrocracked naphtha may be retained in the fin- 6 ished jet fuel by means of pipes 33, 5t} and 34. However, in order to obtain significant improvement in the jet fuel, over the 100 percent hydrocracked product, the naphtha portion of the finished jet fuel should be at least 20 percent straight run naphtha.

The amount of straight run naphtha that is blended with the 350425 F. to 450550 F. material may be substantially equivalent in volume to the volume of the hydrocracked naphtha replaced, i.e., the amount of straight run naphtha may be between and 110 volume percent of the volume of naphtha removed from the process through pipe 33. However, it may be desirable to use a volume of straight run naphtha substantially larger or substantially less than the volume of hydrocnacked naphtha removed. Therefore, within the broad scope of this invention the volume of straight run naphtha in the jet fuel may be Within the range 30 to 300 volume percent of the volume or" hydrocracked naphtha replaced by the straight run naphtha.

In a further embodiment of the process of this invention, the cracked heavy naphtha that is removed through pipe 33 is passed into a suitable catalytic reforming operation 40, that is carried out in the presence of hydrogen. The catalysts utilizable in the reforming operation are well known to those skilled in the art. Thus, the catalysts can be oxides or sulfides of the metals of groups IV, V, VI, VII and VIII of the periodic arrangement of the elements, alone or, as is generally the case, supported upon a carrier, such as alumina, spinels, etc. Such catalysts include molybdenum oxide, chromium oxide, cobalt molybdate, and the like. The reforming conditions used with these catalysts include, usually, temperatures of 750 1150 F. and pressures of 503 000 pounds per square inch gauge.

It is also contemplated to carry out the reforming operation in the presence of hydrogen and of platinumor palladium-containing catalysts. Such catalysts contain between about 0.05 percent and about 2 percent, by weight of the catalyst, of platinum or palladium, or both, deposited upon supports. Suitable supports, or carriers, include mixtures of two or more refractory oxides, such as silica alumina, silica-alurnina-thoria, alu-rnina-boria, etc. Another type of support proposed for platinum reforming catalysts is alumina that has halogen composited therewith, and which may also contain small amounts of silica. The reforming conditions used with these platinumor palladium-containing catalysts include temperatures within the range about 700 F. to about 1000 F., preferably Within the range about 725 F. to about 950 F. The liquid hourly space velocity will be within the range about 0.1 to about 10, preferably within the range about 0.5 to about 4. The hydrogen pressure will be within the range about pounds per square inch gauge to about 1000 pounds per square inch gauge, preferably within the range about 350 to about 700 pounds per square inch gauge. The molar proportion of hydrogen to hydrocarbon charge will be between about 1 and about 20, preferably between about 4 and about 12.

In the reforming operation, there is a net production of hydrogen. This hydrogen can be removed through a pipe 4-1 and can be recycled through pipe 19 to supply at least a portion of the hydrogen consumed in the cracking operation. The reformed naphtha obtained in the reforming operation is removed through a pipe 42 and passed through a gasoline blending operation 43. In this operation, butanes introduced through pipe 3-1 and light naphtha introduced through pipe 32 are blended with the reformate from pipe 42 in suitable proportions to produce the desired octane and vapor pressure gasoline. The finished gasoline is then removed through a pipe 44.

The following examples are illustrative of the process of this invention and of the improved jet fuels and gasolines obtained thereby.

7 EXAMPLE 2 The charge stock used in this example was a gas oil obtained from a Kuwait crude. This Kuwait gas oil had the following properties:

A.P.I. gravity 33.8 Distillation, vacuum assay:

F 467 5 0% F-.. 599 95 F 789 Sulfur, weight percent 1.51 Pour point, F +35 This gas oil was subjected to cracking in the presence of hydrogen and of the platinum catalyst described in Example 1 that had reached equilibrium, i.e., had been in use for more than five days. The cracking operation was carried out at a pressure of 1000 p.s.i.g. using a hydrogento-oil molar ratio of 40 and a liquid hourly space velocity of 0.5, at a temperature of about 730 F. "From this run, there was obtained 73.4 volume percent yield of a jet fuel boiling Within the range about 214 F. to about 524 F. The properties of this jet fuel are set forth in column 2A of Table I.

It was found that about 63 volume percent (46.6 volume percent of the original charge) of this jet fuel boiled in the heavy naphtha boiling range. This portion of the jet fuel was removed and was replaced with a Kuwait straight run naphtha. This Kuwait naphtha had the following properties:

A.P.I. gravity 57.1 A.S.T.M. distillation:

I.B.P. F 188 50% F 289 BR F 408 Sulfur, weight percent 0.084

The resultant blend of Kuwait straight run naphtha with the cracked fraction boiling between about 390 F. and about 480 F. comprised about 64 volume percent straight run naphtha and about 36 volume percent cracked material. Pertinent properties of this jet fuel are set forth in Table I in column 213.

EXAMPLE 3 The charge stock used in this run was another Kuwait gas oil having the following properties:

This gas oil was subjected to cracking in the presence of hydrogen and of the equilibrium platinum catalyst de scribed in Example 1. The run was carried out under a pressure of 1000 p.s.i.g. using a hydrogen-to-oil molar ratio of 40 and a liquid hourly space velocity of 0.5. The temperature employed was about 793 F. Under these conditions there was produced about 66.9 volume percent lower boiling range jet fuel. Pertinent properties of this fuel are set forth in Table 1, column 3A.

About 77 volume percent of this jet fuel boiled in the heavy naphtha boiling range. This portion was removed and replaced with the Kuwait straight run naphtha described in Example 2. The resultant blended fuel contained about 79 volume percent straight run naphtha and about 21 volume percent cracked product. Pertinent properties of this jet fuel are set forth in Table 1, column 3B.

EXAMPLE 4 The charge material used in this run was a refractory cycle stock derived from a conventional cracking operation using silica-alumina catalyst. following properties:

This material had the The cycle stock was subjected to cracking in the presence of hydrogen and of the equilibrium platinum catalyst described in Example 1. The run was carried out 'at a pressure of 1000 p.s.i.g. using a hydrogen-to-oil molar ratio of 40 and a liquid hourly space velocity of 0.5 The temperature employed was about 735 F. Under these conditions there was produced 78.5 volume percent yield of jet fuel. Pertinent properties of this fuel are set forth in Table I, column 4A.

This fuel contained about 67 volume percent material boiling within the heavy naphtha boiling range. This portion was removed and was replaced by a portion of the Kuwait straight run naphtha defined in Example 2. The resultant jet fuel comprised about 68 volume percent straight run naphtha and about 32 volume percent cracked material. The pertinent properties thereof are set forth in Table 1, column 413.

Table I 2A 2B 3A j 3B I 4A 4B i121 Gravit 49.8 52.9 49.5 52.3 45.6 51.0

214. 194 219 190 210 190 278 273 280 270 286 285 340 338 337 340 350 348 456 452 457 450 450 459 524 515 513 514 532 519 -76 76 -70 69 75 Aromatics, v01. Percent 18.7 13.3 18.4 15.0 21.8 17.1 Sulfur, Wt. Percent 0.043 0. 093 0.017 0.081 0.004 0. 059 Aniline-Gravity Product. 6, 525 7,385 6, 300 7, 245 5, 470 6,875 SmokeVolatilityIndex--- 55.7 50.1 54.1 50.5 47.7 55.4

1 Determined by FLA. method.

In Table I the data set forth in the A columns are descriptive of the cracked fuel. The properties of the improved fuel of this invention are set forth in the B columns. By comparison of the data in the A columns with the corresponding B columns (2A with 2B, 3A with BB, 4A with 4B), it will be noted that, in all cases, the properties of the jet fuel have been greatly improved. The aromatic contents are decreased although, surprisingly, the freezing points are essentially unaffected. The aniline-gravity product is greatly increased. This value is a measure of the heat content of a jet fuel and is directly translatable into terms of the number of Btu. per pound. Accordingly, an increased aniline-gravity product denotes that a fuel has a greater heat (energy) value. As will be readily appreciated, this means, for example, that long range jet aircraft can operate over greater distances with no increase in the weight of the fuel carried. It will be also noted that the smoke volatility index is increased in each case. This is a measure of the smoking tendencies of a fuel, the higher value being desirable. In terms of jet engine operation, a high smoke volatility index means that the engine can be operated for longer periods of time before it will be necessary to overhaul the engine and to clean accumulated depsoits of soot and carbon from the combustion chamber and subsequent portions of the engine. These deposits cause operating difficulties by interfering with combustion in the combustion chamber and by damaging the turbine.

It will be noted that substantial amounts of cracked heavy naphtha are made available by the process of this invention. These naphthas, generally, are readily catalytically reformed to produce excellent yields of high octane gasoline. At the same time, in the reforming of these naphthas there are produced great amounts of hydrogen. The straight run naphthas, on the other hand, usually produce lower yields of high octane gasoline when they are subjected to reforming. Likewise, the amount of hydrogen produced when reforming the straight run in reforming the cracked naphtha.

from the following examples.

770 cubic feet per barrel.

a platinum-containing reforming catalyst.

to the reformer.

former of 640 cubic feet (0.466 x 1370).

barrel.

1% in the presence of hydrogen and of the platinum-containing catalyst described in Example 5. The run was carried out using a hydrogen pressure of about 500 pounds per square inch gauge, a hydrogen to hydrocarbon molar ratio of 10, a liquid hourly space velocity of 1.8, and a 5) naphtha is considerably less than the amount produced temperature of 965 F. Under these conditions there was produced a 1045 R.V.P. gasoline having an octane Accordingly, in another embodiment of this invention, number of 95.6 (-F-l|3 cc. TEL), in a yield of 84.2 there is effected the production of high quality jet fuel, volume percent. The amount of hydrogen produced was the production of high octane gasoline in excellent yields, 840 cubic feet per barrel of naphtha charged. Thus, and a better over-all hydrogen balance (as compared to the amount of hydrogen produced in reforming 0.466 processes wherein jet fuel is produced by cracking alone, barrel (the amount of straight run naphtha used in the and the gasoline and hydrogen are obtained by reforming presence of this invention per barrel of original charge) straight run naphtha), by a process that involves cracking was 390 cubic feet.

a gas oil in the presence of hydrogen to produce a jet 1 The embodiment of this invention, wherein the cracked fuel, replacing the heavy naphtha portion of the jet fuel naphtha is replaced by straight run naphtha and the With a Straight full p atalytically reforming the cracked naphtha is reformed, has :a number of advantages cracked naphtha to produce high octane gasoline and over a refinery operation in which the straight run naphtha hydrogen, and recycling the hydrogen to supply at least is reformed and the jet fuel is simply a cracked product. a portion of the hydrogen required in the cracking step. 0 Based upon the data in Examples 5 and 6, the following The many advantages of this Operation Will be pp tabulation demonstrates the advantages. Operation A, the method of this invention, is presented upon the basis of cracking, in the presence of hydrogen, one barrel of EXAMPLE 5 Kuwait gas oil to produce a jet fuel; removing 0.466

In the cracldng operation described in Example 2, there Panel 0f heavy naphtha P f g this in the was produced 73.4 volume percent yield of jet fuel. The l fuel Wlth (1465 barrel of KllWalt Straight 11111 heavy hydrogen consumption in the operation was found to be p reforming the cracked y naphtha Ihat Was removed from the jet fuel; and recycling to the cracking As was described in Example 2, 63 volume percent of P the hydrogen Produchd in the reforming p- P- this fuel, representing 46.6 volume percent based upon eh'ltioh B, for Comparison P p is Presented I1PO11 the original charge, which boiled in the naphtha boiling the basis of cracking. in the presence of hydrogen. one range, was removed This cracked h h was barrel of Kuwait gas oil to produce a jet fuel; reforming jected to reforming in the presence of hydrogen and of (3-465 barrel of Straight T1111 Kuwait heavy P and Th prepara. recycling the hydrogen produced in the reforming step. tion and properties f the f r ing catalyst are f ll The product distribution in each case is shown in Table set forth in Example 2, catalyst E, of copending applica- L tion Serial Number 541,734, filed October 20, 1955. Table H Briefly, the catalyst had a surface area of about 575 square meters per gram and contained 0.38 percent plati- Operation Operation num, by weight of the catalyst, supported upon silica 40 A B that had cogelled therewith 0.4 percent alumina.

The reforming operation was carried out in the presence fi gf gg 734 734 of hydrogen in amounts, expressed as the molar ratio Aniline-Gravity Product 7. 385 6,525 of hydrogen to hydrocarbon charge, of about 10, using g;};, ggj, gf f:: 2% 3 a :hydrogen pressure of about 500 pounds per square Octane N mbe 1+3c TEL) 95.9 95.6 inch gauge, a liquid hourly space velocity of 1.8, and Hydrogen Balance,

a temperature of 903 F. Under these conditions there Consumed ),cu.ft--- 770 770 was obtained a yield of 101 volume percent 10# Reid Pmducedueformmghcmft' 640 390 vapor pressure gasoline having an octane rating of 95.9 Net Consumption, it 130 80 The amount of hydrogen produced was 1370 cubic feet per barrel of naphtha charged The many advantages of this embodiment of the present In terms of the original charge to the invention will be apparent from the data set forth in over-all process, i.e., the charge to the cracking oper- Table 11. These include (1) ajet fuel of superior quality, ation, there was a net production of hydrogen in the re- (2) a greater yield of gasoline of a given octane number,

Thus, in the and (3) a better over-all hydrogen balance. Similar over-all process, including cracking and reforming, the advantageous results can be obtained using other gas oils net consumption of hydrogen was 130 cubic feet per and other cracking and reforming catalysts. In some cases, wherein the amount of jet fuel produced is rela- EXAMPLE 6 tively high, the correspondingly greater amount of cracked 69 naphtha available for reforming can supply sufficient For purposes of comparison, the straight run Kuwait naphtha defined in Example 2 was subjected to reforming hydrogen to balance the amount consumed in the cracking step.

Table III 7A 7B 7C 7D 7E 7F 7G Gravity, A.P.I 50.1 51. 9 53.1 47. 9 48. 8 52.1 55. 4 Naptha, v01. percent of jet fuel 74.1 74.1 74.1 46.1 46.1 89. 5 89. 5 Heavier material, vol. percent of jet fuel 25. 9 25. 9 25.9 53.9 53. 9 10.5 10. 5 Ratio of naphtha/heavier material 2. 86 2.86 2.86 0.85 0. 8. 5 8. 5 Source of naphtha:

Hydrocracked, vol. perceut 160 50 0 100 0 Straight run, vol. percent 0 50 100 0 100 0 100 Amount of naphtha as vol. percent of naphtha in original hydrocracked jet fuel 100 100 100 30 30 300 300 Aniline-gravity Product 6, 954 7, 188 7, 4.07 6, 902 7, 061 6, 981 7, 540

1 1 EXAMPLE 7 The purpose of this example is to demonstrate the broad range of straight run naphtha volumes that may be used within the scope of this invention. A Guico heavy gas oil having the following properties was hydrocracked:

The hydrocracking was conducted over a catalyst consisting of 0.5 weight percent platinum on a silica-alumina base with an activity index of 46, at a temperature of 783 F., a hydrogen pressure of 1500 p.s.i.g., liquid hourly space velocity of 0.5 and 14,500 standard cubic feet of hydrogen per barrel of charge in the reaction zone. This reaction produced 62.2 volume percent of jet fuel with the properties listed in column 7A of Table III. A Kuwait straight run naphtha was used to replace the hydrocracked naphtha portion in varying amounts. The results of this are given in columns 73, 7C, 7E and 76 of Table III. The properties of jet fuels employing hydrocracked naphtlia in different proportion than in the original hydrocracked jet fuel are given in columns 7D and 7F of Table III for comparison purposes. The Kuwait straight run naphtha used had the following properties:

The jet fuels whose properties are listed in columns 7A, 7B and 7C of Table III may advantageously be compared. Column 7A gives the properties of the unaltered hydrocracked jet fuel, column 7B the properties of jet fuel prepared by replacing one-half of the hydrocracked naphtha in the jet fuel with an equivalent amount of stnaight run naphtha and column 70 gives the properties of the jet fuel with all of the hydrocracked naphtha replaced by the same volume of straight run naphtha. It will be noted that the two jet fuels containing straight run naphtha have the same total naphtha content, 74.1 volume percent, as the jet fuel separated from the hydrocracked product. This comparison shows that replacement of one-half of the hydrocracked naphtha with straight run naphtha increases aniline-gravity product by 234 while replacing all of the hydrocracked naphtha increases the aniline-gravity product by 453. It is evident, therefore, that in this invention less than all of the hydrocracked naphtha may be replaced with straight run naphtha and substantial improvement in the jet fuel obtained. The greatest improvement occurs when all of the hydrocracked naphtha is replaced with straight run. In order to obtain any significant advantage from this invention, however, suflicient straight run naphtha should be introduced into the jet fuel so that at least volume percent of the naphtha portion of the jet fuel is straight nun naphtha.

A comparison may also be made among the jet fuels Whose properties are listed in columns 7A, 7D and 7E of Table III. The jet fuels of 7D and 7E have an amount of naphtha only volume percent of the amount in the jet fuel fraction produced by the hydrocracking operation (7A) Without change in the amount of heavier cracked material. The naphtha in these two fuels amounts to 46.1 volume percent of the total. Comparison of 7A and 7D shows that reducing the percentage of naphtha in the jet fuel reduces the aniline-gravity product. However, when the hydrocracked naphtha is replaced by straight r-un naphtha even if the straight run naphtha is only 30 volume percent of the hydrocracked naphtha in the original jet fuel (compare 7A and 7E), there is an improvement of 107 in the aniline-gravity product.

Comparison may also be made among 7A, 7F and 7G. In the latter two, the volume of naphtha in the jet fuel is increased to 300 volume percent of the naphtha volume of the jet fuel produced by hydrocracking alone so that naphtha forms 89.5 volume percent of the total jet fuel. The increase in naphtha content increases somewhat the aniline-gravity product even when all of the naphtha is hydrooracked -(7A and 7F). However, when this invention is employed and straight run naphtha substituted for hydrocracked naphtha (76), the aniline-gravity product is increased by 586 over the material produced by the hydrocracked naphtha (7A) and by 559 over the jet fuel with the same volume of hydrocracked naphtha (7F).

Within the broad scope of this invention the hydrocracked naphtha removed from the jet fuel produced by hydrocracking may be replaced by a volume of straight run naphtha amounting to 30 to 300 volume percent of the hydrocracked naphtha provided, as indicated above, that the straight run naphtha amounts to at least 20 volume percent of the total naphtha in the jet fuel. The volumetric ratio of naphtha to material heavier than naphtha (boiling from 350425 F. to 450-550 F.) in the finished jet fuel may be Within the range 0.85 to 8.5.

Although the present invention has been described with preferred embodiments, it is to be understood that modifications and variations may be resorted to, without departing from the spirit and scope of this invention, as those skilled in the art Will readily understand. Such variations and modifications are considered to be within the purview and scope of the appended claims.

We claim:

1. A process for producing a novel jet fuel, which comprises: contacting a distillate hydrocarbon fraction having an initial boiling point greater than 400 F. and "a 50 percent point greater than 500 F. with a hydrocracking catalyst, in the presence of hydrogen under hydrocracki-ng reaction conditions to convert at least a portion of said fraction, with a net consumption of hydrogen into a jet fuel having an initial boiling point within therange about F. to about 225 F. and an end boiling point within the range about 450 F. to about 550 F.; separating from said jet fuel at least a substantial part of the cracked naphtha fraction with an initial boiling point within the range about 160 F. to about 225 F. and an end boiling point within the range about 350 F. to about 425 F., and replacing said portion of the cracked naphtha fraction in the jet fuel with a straight run distillate naphtha having an initial boiling point within the range about 160 F. to about 225 F. and an end boiling point within the range about 350 F. to about 425 F., the amount of straight run naphtha used being between 30 and 300 percent of the volume of cracked naphtha which it replaces and being sufiicient in quantity that the naphtha portion of the completed jet fuel is at least 20 voiume percent straight run naphtha.

2. The process of claim 1 further limited to removing from the hydrocnacked jet fuel all of the cracked naphtha fraction with an initial boiling point Within the range about 160 F. to about 225 F. and an end boiling point within the range about 350 F. to about 425 F. and replacing said fraction with a straight run naphtha having an initial boiling point within the range about 160 F. to about 225 F. and an end boiling point within the range about 350 F. to about 425 F the volume of said straight run naphtha used being between about 30 and about 300 percent of the volume of the cracked naphtha fraction.

3. The process of claim 1 further limited to the hydrocracking being conducted over a catalyst which comprises between about 0.05 and 20 percent by Weight of the catalyst of at least one metal of the platinum and palladium series deposited upon a composite of solid oxides of at least two elements of groups HA, IIIB and IV of the periodic arrangement of elements, said synthetic composite having an activity index of at least 25.

4. A process for producing a novel jet fuel that comprises contactins a distillate hydrocarbon fraction having an initial boiling point greater than about 400 F., a 50 percent point greater than about 500 P. with a hydrocracking catalyst, vin the presence of hydrogen, in amounts expressed in molar ratio of hydrogen to hydrocarbon charge, within the range about 2 to about 80, under hydrocracking conditions to convert at least a portion of the hydrocarbon charge into a jet fuel having an initial boiling point falling within the range about 160 F. to about 225 F. and an end boiling point falling within the range about 450 F. to about 550 F.; separating from said fuel the cracked naphtha fraction that has an initial boiling point falling within the range about 160 F. to about 225 F. and an end boiling point falling within the range about 350 F. to about 425 F., and replacing said cracked naphtha fraction in the jet fuel with a straight run distillate naphtha that has an initial boiling point falling within the range about 160 F. to about 225 F. and end boiling point falling within the range about 350 F. to about 425 F, the amount of straight run naphtha used being between about 90 percent and about 110 percent of the volume of the cracked naphtha.

5. A method for producing a novel jet fuel that comprises contacting a gas oil having an end boiling point greater than about 760 F. with a catalyst comprising between about 0.05 percent and about 20 percent, by weight of the catalyst of at least one metal of the platinum and palladium series deposited upon a synthetic composite of solid oxides of at least two elements of groups EA, 11113 and IV of the periodic arrangement of elements, said synthetic composite having an activity index of at least 25, in the presence of hydrogen in amounts, expressed in the molar ratio of hydrogen to hydrocarbon charge, within the range about 2 to about 80, at pressures Within the range about 100 p.s.i.g. to about 2500 p.s.i.g., at a liquid hourly space velocity within the range about 0.1 to about 10, and at temperatures falling within the range about 500 F. to about 825 F., and correlating said temperature with said liquid hourly space velocity to convert at least a portion of the hydrocarbon charge into a jet fuel having an initial boiling point falling within the range about 160 F. to about 225 F. and an end boiling point falling within the range about 450 F. to about 550 F.; separating from said fuel the cracked naphtha fraction that has an initial boiling point falling within the range about 160 F. to about 225 F. and an end boiling point falling within the range about 350 F. :to about 425 F, and replacing said cracked naphtha fraction in the fuel with a straight run distillate naphtha that has an initial boiling point falling within the range about 160 F. to about 225 F. and an end boiling point falling within the range about 350 F. to about 425 F.,

14 the amount of straight run naphtha used being between about percent and about percent of the volume of the cracked naphtha.

6. A method for producing a novel jet fuel that comprises contacting a gas oil having an end boiling point greater than about 760 F. with a catalyst that comprises between about 0.1 percent and about 5 percent platinum, by weight of the catalyst, deposited upon a synthetic composite of silica and alumina that has an activity index of at least 28, in the presence or" hydro-gen in amounts, expressed in molar ratio to hydrogen to hydrocarbon charge, within the range about 5 to about 50, at pressures Within the range about 350 p.s.i. g. to about 2000 p.s.i.g., at a liquid hourly space velocity within the range about 0.1 to about 5, and at a temperature falling within the range about 600 F. to about 775 F. and correlating said temperature with said liquid hourly space velocity to convert at least a portion of the hydrocarbon charge into a jet fuel having an initial boiling point falling within the range about F. to about 225 F. and an end boiling point falling within the range about 450 F. to about 550 F.; separating from said fuel the cracked naphtha fraction that has an initial boiling point falling within the range about 160 F. to about 225 F. and an end boiling point falling within the range about 350 F. to about 425 F. and replacing said cracked naphtha fraction in the fuel with a straight run distillate naphtha that has an initial boiling point falling within the range about 160 F. to about 225 F., and an end boiling point falling within the range about 350 F. to about 425 F., the amount of straight run naphtha used being between about 90 percent and about 110 percent of the volume of the cracked naphtha.

7. A process as described in claim 6 wherein said hydrocarbon fraction is a Kuwait gas oil and said straight run naphtha is a Kuwait naphtha.

8. A process as described in claim 6 wherein said gas oil is a refractory cycle stock and said straight run naphtha is a Kuwait naphtha.

References Cited in the file of this patent UNITED STATES PATENTS 2,749,225 Barnum et al. June 5, 1956 2,910,426 Gluesenhamp et al Oct. 27, 1959 2,945,801 Ciapetta et a1 July 19, 1960 2,945,802 Ciapetta et a1. July 19, 1960 3,015,549 Ciapetta et al. Jan. 2, 1962 OTHER REFERENCES Petroleum Processing, October 1952, pp. 1425 to 1429.

Jet Fuels, The Petroleum Engineer, November 1952, pp. C7 to C10. 

1. A PROCESS FOR PRODUCING A NOVEL JET FUEL, WHICH COMPRISES: CONTACTING A DISTILLATE HYDROCARBON FRACTION HAVING AN INITIAL BOILING POINT GREATER THAN 400*F. AND A 50 PERCENT POINT GREATER THAN 500*F. WITH A HYDROCRACKING CATALYST, IN THE PRESENCE OF HYDROGEN UNDER HYDROCRACKING REACTION CONDITIONS TO CONVERT AT LEAST A PORTION OF SAID FRACTION, WITH A NET CONSUMPTION OF HYDROGEN INTO A JET FUEL HAVING AN INITIAL BOILING POINT WITHIN THE RANGE ABOUT 160*F. TO ABOUT 225*F. AND AN END BOILING POINT WITHIN THE RANGE ABOUT 450*F. TO ABOUT 550*F.; SEPARATING FROM SAID JET FUEL AT LEAST A SUBSTANTIAL PART OF THE CRACKED NAPHTHA FRACTION WITH AN INITIAL BOILING POINT WITHIN THE RANGE ABOUT 160*F. TO ABOUT 225*F. AND AN END BOILING POINT WITHIN THE RANGE ABOUT 350*F. TO ABOUT 425*F., AND REPLACING SAID PORTION OF THE CRACKED NAPHTHA FRACTIN IN THE JET FUEL WITH A STRAIGHT RUN DISTILLATE NAPHTHA HAVING AN INITIAL BOILING POINT WITHIN THE RANGE ABOUT 160*F. TO ABOUT 225*F. AND AN END BOILING POINT WITHIN THE RANGE ABOUT 350*R. TO ABOUT 425*F., THE AMOUNT OF STRAIGHT RUN NAPHTHA USED BEING BETWEEN 30 AND 300 PERCENT OF THE VOLUME OF CRACKED NAPHTHA WHICH IT REPLACES AND BEING SUFFICIENT IN QUANITY THAT THE NAPHTHA PORTION OF THE COMPLETED JET FUEL IS AT LEAST 20 VOLUME PERCENT STRAIGHT RUN NAPHTHA. 